Electronic article surveillance (EAS) systems for detecting and preventing theft or unauthorized removal of articles or goods from retail establishments and/or other facilities, such as libraries, have become widespread. In general, such security systems use a security tag which is secured to or associated with an article (or its packaging), typically an article which is readily accessible to potential customers or facility users and, therefore, is susceptible to unauthorized removal. In general, such EAS systems are employed for detecting the presence (or the absence) of a security tag and, thus, a protected article within a surveilled security area or detection zone, also referred to herein as an "interrogation zone". In most cases, the detection zone is located at or around an exit or entrance to the facility or a portion of the facility.
One type of EAS system which has gained widespread popularity uses a security tag which includes a self-contained, passive resonant circuit in the form of a small, generally planar printed circuit which resonates at a predetermined detection frequency within a detection frequency range. A transmitter, which is also tuned to the detection frequency, transmits electromagnetic energy or an interrogation signal into the detection zone. A receiver, tuned to the detection frequency, is positioned proximate to the detection zone. Typically, the transmitter and a transmitter antenna are located on one side of an exit or aisle and the receiver and a receiver antenna are located on the other side of the exit or aisle, so that a person must pass between the transmitter and receiver antennas to exit the facility. When an article having an attached security tag moves into or passes through the detection zone, the security tag is exposed to the transmitted energy (the security tag is interrogated), resulting in the resonant circuit of the tag resonating to provide an output signal detectable by the receiver. The detection of such an output signal by the receiver indicates the presence of an article with a security tag within the detection zone and the receiver activates an alarm to alert appropriate security or other personnel.
One well-known EAS system has a transmitting and detecting frequency in the radio frequency range. The security tags used with such systems are referred to as RF tags or RF security tags. The RF tags associated with each article may be identical so that all articles, regardless of size or value, which include the security tag return an identical signal to the receiver. Alternatively, the RF tags may be passive resonant security tags which return unique or semi-unique identification codes. U.S. Pat. No. 5,446,447 (Carney et al.), U.S. Pat. No. 5,430,441 (Bickley et al.), and U.S. Pat. No. 5,347,263 (Carroll et al.) disclose three examples of such security tags. These security tags typically include an integrated circuit to generate the identification code. Such "intelligent" security tags provide additional information about the article detected in the zone of the interrogator. These intelligent security tags typically respond to, and transmit signals, in the radio frequency range, and are known in the art as "radio frequency identification (RFID) tags or "intelligent security tags." RFID tags are used in RFID systems. Intelligent security tags may also resonate at non-RF frequency bands, and may be referred generically as "EAS markers."
Existing EAS systems of the type described above and of other types have been shown to be effective in preventing the theft or unauthorized removal of articles.
As noted above, security tags are secured to or associated with an article (or its packaging). This process, referred to herein as "tagging" the article is typically performed in a retail store by store employees. To reduce personnel costs and errors caused by store employees, some retail establishments are insisting that articles be tagged before they arrive at the store or a store distribution center. Furthermore, some manufacturers are pretagging articles with intelligent RFID tags before shipment to allow for lifecycle tracking of the article. One method for achieving the desired pretagging is to tag the articles during or after the assembly process, or as they are prepared for packaging or shipment from the manufacturer or manufacturer's distribution center.
One issue associated with such pretagging is that there needs to be some assurance that the security tag was properly applied to the article or packaging and that the security tag is in a functional state, since the receiving stores or other facilities may no longer verify the existence of active security tags on presumably pretagged articles. Thus, if the store's EAS system does not detect any security tags as a customer exits the store, it is presumed that the security tags on any purchased items were properly deactivated or removed. The conventional EAS system cannot detect a failure by the manufacturer to tag the articles with a properly functioning tag.
The present invention fulfills this need by providing a system which verifies proper tagging and proper functioning of the tag at the tag application source.